Many current semiconductor processes are performed at a temperature that is different than ambient temperature. For example, certain processes may be best performed in a cold environment, such as below 0° C., while others are best performed in a hot environment, such as above 500° C. Often, it is not the temperature of the ambient environment, but rather the actual temperature and/or the temperature uniformity of the workpiece that is of interest. Thus, monitoring the temperature of the workpiece itself may be beneficial.
Techniques for workpiece temperature measurement are limited by the parameters of the processing environment. For example, thermocouples attached to the workpiece are impractical if the workpiece moves. Alternatively, thermocouples mounted to the supporting structure are of limited use, as the temperature of the supporting structure may differ from that of the workpiece due to problems associated with establishing good thermal contact between the supporting structure and the workpiece. Additionally, the optical properties of silicon make the application of common infrared techniques difficult or impossible. Specifically, at certain temperatures, silicon is nearly transparent at infrared frequencies, making it difficult to determine the actual temperature of the workpiece. Rather, in these instances, the infrared system is often monitoring the temperature of the surfaces adjacent to the workpiece, rather than the workpiece itself.
In some semiconductor processing devices, the workpieces may be rotated relative to an aperture, so that only a portion of the total workpiece is visible at any particular time. Thus, monitoring the temperature of the workpieces is further complicated by the inability to continuously monitor the entire workpiece.
Thus, any system or method that allows for measurement of the temperature of a workpiece in a process chamber would be beneficial. Further, it would be beneficial if the temperature of multiple workpieces within a rotating semiconductor processing device could be monitored simultaneously.